Integral multiple stage safety valves

Abstract

An integral multistage safety valve is designed to provide a second level of protection should a first stage fail. The valve may be used in oil and/or gas wells. The interior portion of the multiphase safety valve is designed so as to reduce turbulence and pressure loss through the valve when the valve is in an open position. The valves may be independently operable, or operable with a single control line. The multi-stage valve reduces the number of body joints required to construct two identical valves thereby reducing cost and potential leak paths and increasing reliability of the system.

We claim: 
     
       1. An integral multistage safety valve for an oil or gas well comprising:
 a first valve including a spring housing having a valve seat at a lower end, and a sliding sleeve; 
 an integral chamber housing connected to the first valve at one end and having a first interior chamber that receives a lower end of the sliding sleeve and the valve seat of the first valve; 
 the integral chamber housing having an interior bore for slidably receiving a piston actuator; and 
 a second valve having a spring housing and a sliding sleeve, the second valve connected to the integral chamber housing at a second end of the integral chamber housing, a portion of the sliding sleeve received within a second chamber of the integral chamber housing. 
 
     
     
       2. A valve according to  claim 1  further including an upper connection body coupled to the first valve and a lower connection body coupled to the second valve, the upper connection body including as bore for receiving a piston actuator and the lower connection body surrounding a lower portion of the sliding sleeve and the valve seat of the second valve. 
     
     
       3. A valve according to  claim 1  wherein the sliding sleeves of the valves and an internal flow passage of the integral chamber housing form a substantially constant diameter flow path when the valves are in the open position to substantially reduce turbulence and pressure loss. 
     
     
       4. A valve according the  claim 1  wherein each valve includes a spring housing, a sliding flow sleeve, a piston connected to the sliding flow sleeve and a spring biasing the sliding flow sleeve in an upward direction. 
     
     
       5. A valve according to  claim 4  wherein the valve further includes a flapper valve pivotably mounted on a downstream portion of the spring housing. 
     
     
       6. The valve according to  claim 1  wherein the integral chamber housing includes two tubular members connected together. 
     
     
       7. An integral multistage safety valve for an oil or gas well comprising:
 a first valve including a spring, housing; 
 a second valve including a second spring housing; 
 an integral chamber housing having an interior flow passage connected between the first and second valves, said valves being hydraulically operated by a single control line extending to the surface of the well, and a branch line extending to the first valve and a flow restrictor in the branch line or in the control line downstream of the branch line. 
 
     
     
       8. The valve according to  claim 7  further including:
 an upper connection member connected to the first valve; and 
 a lower connection member connected to the second valve, 
 
     
     
       9. The valve according to  claim 8  wherein the first and second valves, the integral chamber housing and the upper and lower connection members have interior flow passages of substantially the same diameter to reduce turbulence and pressure loss. 
     
     
       10. The valve according to  claim 7  wherein the valves are independently operable. 
     
     
       11. The valve according to  claim 10  including a hydraulically operated piston actuator for each valve and separate hydraulic hues for each piston actuator. 
     
     
       12. The valve according to  claim 7  including no more than four body joints. 
     
     
       13. The valve according to  claim 7  wherein said body joints are of the same thread form.